It has long been known that calcium is a required nutriment for the human body. Frequently calcium carbonate (CaCO.sub.3) is used as a dietary supplement to provide the needed calcium. In part, this is due to the fact that calcium carbonate is more easily solubilized in the gastrointestinal tract than are many other calcium salts, due to its solubility in acidic solutions.
Some individuals have trouble taking calcium carbonate in solid form. For certain of these individuals, the problem is simply a matter of physical difficulty with ingesting CaCO.sub.3 tablets, which may be large or hard to chew. Others may find the taste unacceptable.
Still others appear to lack sufficient acid in their gastrointestinal juices to ensure solution. Such individuals may excrete most ingested calcium carbonate, without sufficient absorption. See for instance, Ivonovich, Fellows and Rich, "The Absorption of Calcium Carbonate", Annals of Internal Medicine, Volume 66, No. 5, pp. 917-923 (May 1967).
If water-insoluble calcium carbonate cannot be converted to the soluble calcium chloride form in vivo, a soluble form of calcium must be administered. Also, a solution of calcium will be preferred by those individuals who have difficulty ingesting solid CaCO.sub.3 tablets.
An approach developed to accomplish solubilization of calcium carbonate, in an orally administered aqueous solution, has been through the development of an effervescent system. Effervescent antacids are well-known, an example being ALKA-SELTZER PLUS disclosed in the U.S. Pat. No. 4,083,950. Such systems generally include an alkaline material, such as sodium bicarbonate, sodium carbonate, potassium bicarbonate, or potassium carbonate, in combination with an organic acid such as citric acid, fumaric acid, or adipic acid. When such a system is placed in water, the carbonate and the acid react to form carbon dioxide and a water soluble salt of the alkali metal cation
An efficient effervescent system, analogous to the antacids but for the delivery of calcium carbonate, comprises calcium carbonate granules compressed into a tablet with an organic acid preferred effervescent composition of this type comprises, by weight: approximately 90-10% CaCO.sub.3 ; 10 to 90% organic acid component; and 2 to 20% compression-enhancing vehicle. (U.S. Pat. No. 4,650,669)
The compression-enhancing vehicle assists tablet formation, while protecting the carbonate/acid couple from premature reaction. It is preferably a substance such as lactose, which can form a coating on the calcium carbonate.
The organic acid is preferably, by weight, at least 80% citric acid. A reason for this is a preference, by most individuals, for the taste of citric acid and its salts.
Flavorings such as grapefruit, lemon and orange may be added to such compositions improve taste. Also, sweeteners, lubricants, vitamins and other adjuvants may be included.
Aspartame is a desired sweetener for utilization in such solutions. It is a widely used low-calorie sugar substitute, typically prepared from L-aspartic acid and L-phenylalanine. It is available under the trade name NutraSweet.RTM. from G. D. Searle and Co., Chicago, Ill.
In use, one or more calcium carbonate-containing effervescent tablets are dissolved in water, to be orally taken by the subject. It has been found that when aspartame is added to such tablets, the effervescent system is adversely affected. In particular, when the aspartame is present in sufficient amount to serve as an effective sweetener, filming occurs; that is, an undesirable film forms. The film tends to adhere to, and climb, the sides of a container in which the effervescence takes place. Such a film is aesthetically undesirable. Further, it may adversely affect taste and texture, and it may hinder complete solution of all constituents of the tablet.
It is desirable to utilize the low calorie sweetener aspartame in calcium carbonate-containing effervescent compositions. Therefore, there is a need for a method by which aspartame may be included in such compositions with control of film formation.